DocumentType: before() method
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2018.
TheDocumentType.before() method inserts a set ofNode objects or strings in the children list of theDocumentType's parent, just before theDocumentType.Strings are inserted as equivalentText nodes.
Syntax
js
before(param1)before(param1, param2)before(param1, param2, /* …, */ paramN)Parameters
param1, …,paramNA set of
Nodeobjects or strings to insert.
Return value
None (undefined).
Exceptions
HierarchyRequestErrorDOMExceptionThrown when the node cannot be inserted at the specified point in the hierarchy.
Examples
Adding a conditional comment
Comment nodes are valid before doctype declarations but not advisablegiven they trigger quirks mode in IE. Aconditional commentworks for IE as well, though:
js
let docType = document.implementation.createDocumentType("html", "", "");let myDoc = document.implementation.createDocument("", "", docType);docType.before( document.createComment("<!--[if !IE]> conditional comment <![endif]-->"),);myDoc.childNodes;// NodeList [<!--[if !IE]> conditional comment <![endif]-->, <!DOCTYPE html>]Specifications
| Specification |
|---|
| DOM # ref-for-dom-childnode-before① |